1. Dietary specializations are important determinants of ecological structure, particularly in species with high per-capita trophic influence like marine apex predators. These species are, however, among the most challenging in which to establish spatiotemporally integrated diets.
2. We introduce a novel integration of stable isotopes with a multidimensional nutritional niche framework that addresses the challenges of establishing spatiotemporally integrated nutritional niches in wild populations, and apply the framework to explore individual diet specialization in a marine apex predator, the white shark (Carcharodon carcharias).
3. Sequential tooth files were sampled from juvenile white sharks to establish individual isotopic (δ-space; δ¹³C, δ¹⁵N, δ³⁴S) niche specialization. Bayesian mixing models were then used to reveal individual-level prey (p-space) specialization, and further combined with nutritional geometry models to quantify the nutritional (N-space) dimensions of individual specialization and their relationships to prey use.
4. Isotopic and mixing model analyses indicated juvenile white sharks as individual specialists within a broader, generalist, population niche. Individual sharks differed in their consumption of several important mesopredator species, which suggested among-individual variance in trophic roles in either pelagic or benthic food webs. However, variation in nutrient intakes was small and not consistently correlated with differences in prey use, suggesting white sharks as nutritional specialists and that individuals could use functionally and nutritionally different prey as complementary means to achieve a common nutritional goal.
5. We identify how degrees of individual specialisation can differ between niche spaces (δ-, p- or N-space), the physiological and ecological implications of this, and argue that integrating nutrition can provide stronger, mechanistic links between diet specialisation and its intrinsic (fitness/performance) and extrinsic (ecological) outcomes. Our time-integrated framework is adaptable for examining the nutritional consequences and drivers of food use variation at the individual, population or species level.

Isotope ratio mass spectrometry was used to measure carbon, nitrogen and sulfur stable isotope signatures in collagen extracted from rows of teeth of white sharks (Carcharodon carcharias), and in tissues (muscle, blubber) of their prey species (teleosts, cephalopods, sharks, rays, whales and dolphins). Tooth collagen was extracted via demineralization of whole teeth using ethylenediaminetetraacetic acid. Isotopic signatures of prey tissues (muscle, blubber) were measured on bulk samples (not lipid extracted). All samples were collected off central New South Wales, Australia, between 2010 and 2020.

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